It is noteworthy that the principal art in the field of this invention was generated during the first several years of the twentieth century, the latest pertinent patents located in our novelty search having been dated in 1934. This indicates that the state-of-the-art in this field is little improved since then, with nothing of relative significance having been accomplished in over fifty years.
It has long been an accepted principle within the vehicle steering field that the so-called Ackermann principle should be followed in the design of steering linkage mechanisms. In general, that principle holds that a projection of the turning axes of the two turning steering wheels intersect one another at a point along a projection of the common axis of the rear wheels, the theory being that this will result in a pure rolling motion of the wheels. However, as described by R. B. Kozmier in his 1962 paper entitled, "Using of Computers in Steering Geometry Analysis," presented to the Society of Automotive Engineers, the Ackermann principle further holds that "a given steering linkage gives perfect steering for only one turning angle of the wheels." Error in other turning angles is indicated as being introduced by the relative lengths and inclinations of the steering arms, the requirement for best operation being "the selection of the proper combination of tie rod and steering arm lengths that will minimize the error throughout the steering range."
Otherwise stated, it will become immediately apparent that adoption of the Ackermann principle in the design of a vehicle steering mechanism will result in a system wherein the desired "pure rolling motion" is absent during all turning angles except one; and that wheel skidding, tire scuffing and steering controllability will occur to an ever increasing extent as the angle of turn away from that single pure turning angle increases. It will also be apparent that there is a finite wheel turning range within which substantial improvements can be made.
In view of the foregoing an important objective of the present invention is to reduce tire scuffing in turns and to improve the general steering characteristics of the vehicle.
The prior art patents mentioned briefly above almost universally discuss and apply the Ackermann principle, but describe mechanisms and detailed components differing from one another in varying degree. Indeed, the 1878 U.S. Pat. No. 205,330, directed to a Velocipede, was issued to Mr. H. Ackermann himself, although it does not set forth the principle which ultimately bore his name. The first recitation of the Ackermann principle appears in U.S. Pat. No. 663,986, issued in 1900, the principle being set forth in some detail therein, although it is not so identified.
Other patents located include U.S. Pat. Nos. 687,588, 686,684, 695,222, 714,501, 690,802, 723,975, 743,013, 1,058,758, 1,111,693, 1,223,469, U.S. Pat. No. Re. 14,385, U.S. Pat. Nos. 1,315,126, 1,551,711, 1,766,506, 1,768,347, 1,787,345, 1,942,263, and 1,775,624, several of which describe the Ackermann principle in some detail. The others are variously directed to mechanisms and components of various types to improve steering and vehicle handling qualities.